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Shuumatsu/ChurchNumberals.hs

Created October 9, 2017 08:15
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ChurchNumberals.hs
module ChurchNumberals where
type ChurchNumberals a = (a -> a) -> a -> a
one :: ChurchNumberals a
one f = f
two :: ChurchNumberals a
two f = f . f
chToInt :: ChurchNumberals Int -> Int
chToInt c = c (+ 1) 0
x' = chToInt one
y' = chToInt two
add' :: ChurchNumberals a -> ChurchNumberals a -> ChurchNumberals a
add' x y = \s z -> x s $ y s z
multiply' :: ChurchNumberals a -> ChurchNumberals a -> ChurchNumberals a
multiply' x y = x . y
-- https://courses.edx.org/courses/course-v1:DelftX+FP101x+3T2015/courseware/5240e299c3604e319986d1d8b3459a5a/f615a291386049d7abcee669b5e3d75c/?child=first
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